If you are licensed for Cognos Visualizer, you might be able to consolidate
more than one reports (coming from mutiple datacubes) in a single dashboard.
However, the reports should be at summary level (not too detailed and
exceeding more than one page). Another alternative would be using Upfront
and openning each report on a seperate EI window (which can be set at
personalized settings). By doing so you can launch both Tabular and ROI
reports on a seperate IE window and fit both them in a same screen.

Unfortunately, if you are limited to use only PowerPlay Window, your options
are not too many. The most you can do is to educate your users on how to use
horizontal and vertical tiling. By doing so they can create (or you can
create pre-formatted ppx for them) different versions of data cubes (ROI,
financial data) and presented in a single screen by tiling them.